1. Types of Rocks
Junior Science

2. Types of Rocks Rocks are classified according to how they were formed.
This results in three main types of rocks: igneous, sedimentary and metamorphic.

3. The Rock Cycle!

4. The Rock Cycle
Rock cycle clip...

5. Igneous Rocks Igneous comes from the Latin word ignis, meaning ‘fire’.
Igneous rocks are formed when molten material from within the Earth cools and becomes solid.
Molten material is called magma when it is below the Earth’s surface, and lava when it is above the Earth’s surface.
Magma reaches the Earth’s surface when volcanoes erupt.

6. Intrusive Igneous Rock
When magma cools slowly below the Earth’s surface it forms intrusive rocks.
Granite is an example of a slow-cooling igneous rock in which crystals can be seen with the naked eye.

7. Extrusive Igneous Rock
Lava cools more quickly than underground magma because it is above the Earth’s surface.
Cooling lava forms extrusive rock.
Crystals formed are small or non-existent. Basalt is an example of an extrusive igneous rock containing tiny crystals.

9. What are igneous rocks used for?
Igneous rocks are extremely hard and are useful building materials.
Bluestone is one example, used in Melbourne for constructing buildings, gutters and laneways.

10. What are igneous rocks used for?
Ancient tools made from igneous rocks have been found in Australia.
Indigenous Australians used greenstone to make axes

11. Sedimentary Rocks
Name comes from Latin words sedimentum, meaning ‘settling’, and sedere, meaning ‘to sit down’.
Made from sediment which is small, broken-down bits of other rocks and the remains of animals and plants.
Sediment is compressed and stuck together in a process known as lithification.

12. Lithification Step 1: Sediment builds up to form a layer.
Pressure from the material above squeezes out any air or gaps.
The particles interlock.
Step 2:
Water seeps through the sediment carrying with it minerals that cement the particles together even more strongly.

13. Types of Sedimentary Rocks

14. Sedimentary Rocks

15. Uses of Sedimentary Rocks
Easy to split
Sandstone used in building and paving materials
Limestone can be ground up to make cement
Coal is burnt to produce electricity

16. Metamorphic Rocks Metamorphic means ‘to change form’
Rocks may be changed by heat and pressure within the Earth
A rock made this way is stronger than the original material because its particles are fused together.

17. Metamorphic Rocks
Slate and Marble are two examples of metamorphic rocks.

18. To be continued...